Hydraulic fracturing additive, hydraulic fracturing treatment fluid made therefrom, and method of hydraulically fracturing a subterranean formation

ABSTRACT

For hydraulic fracturing treatment to increase productivity of subterranean hydrocarbon bearing formation, a hydraulic fracturing additive including a dry mixture of water soluble crosslinkable polymer, a crosslinking agent, and a filter aid which is preferably diatomaceous earth. The method of forming a hydraulic fracturing fluid includes contacting the additive with water or an aqueous solution, with a method of hydraulically fracturing the formation further including the step of injecting the fluid into the wellbore.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to hydraulic fracturing additivesand to methods of making such additives, to hydraulic fracturingtreatment fluids made therefrom and methods of making such fluids, tomethods of modifying a well fluid with such additives and/or fluids, tomethods of operating a well with such additives and/or fluids, tomethods of hydraulically fracturing a well with such additives and/orfluids. In another aspect, the present invention relates to hydraulicfracturing additives comprising polymer, crosslinking agent, a filteraid, and optionally reinforcing materials and to methods of making suchadditives, to hydraulic fracturing treatment fluids made therefrom andmethods of making such fluids, to methods of modifying a well fluid withsuch additives and/or fluids, to methods of operating a well with suchadditives and/or fluids, to methods of hydraulically fracturing a wellwith such additives and/or fluids. In even another aspect, the presentinvention relates to hydraulic fracturing additives comprising a drymixture of polymer, crosslinking agent, a filter aid, and optionallyreinforcing materials and to methods of making such additives, tohydraulic fracturing treatment fluids made therefrom and methods ofmaking such fluids, to methods of modifying a well fluid with suchadditives and/or fluids, to methods of operating a well with suchadditives and/or fluids, to methods of hydraulically fracturing a wellwith such additives and/or fluids. In still another aspect, the presentinvention relates to hydraulic fracturing fracturing additivescomprising polymer and diatomaceous earth (“DE”) and to methods ofmaking such additives, to hydraulic fracturing treatment fluids madetherefrom and methods of making such fluids, to methods of modifying awell fluid with such additives and/or fluids, to methods of operating awell with such additives and/or fluids, to methods of hydraulicallyfracturing a well with such additives and/or fluids.

[0003] 2. Description of the Related Art

[0004] The productivity or injectivity of a wellbore in fluidcommunication with a subterranean hydrocarbon-bearing formation may beundesirably low due to a number of causes, including low permeability ofthe formation rock, placement of casing cement, plugging by previouslyinjected materials, clay damage, or produced fluid damage. Productivityor injectivity may be increased by hydraulically fracturing theformation.

[0005] Hydraulic fracturing generally entails injecting a fluid into thewellbore at a sufficient rate and pressure to overcome the tensilestrength of the formation and the overburden pressure. The injectedfluid creates cracks or fractures extending from the wellbore out intothe formation which are usually propped open with a solid proppantentrained in the fluid. The fractures permit the flow of hydrocarbonsand other fluids into or out of the wellbore.

[0006] U.S. Pat. No. 3,816,151 to Podlas, U.S. Pat. No. 3,938,594 toRhudy et al and U.S. Pat. No. 4,137,182 to Golinkin disclose hydraulicfracturing processes using a number of crosslinked polymer solutions asfracturing fluids.

[0007] U.S. Pat. No. 4,779,680, issued Oct. 25, 1988 to Sydansk, notesthat many of the then prior art crosslinking reactions prescribed werevery difficult to control. Sydansk further notes that uncontrolledcrosslinking can occur too rapidly, producing a non-homogeneoussuspension of highly viscous gel balls in a watery solution, or in theother extreme crosslinking can fail to occur at all. In either case, theresult is an ineffective fracturing fluid.

[0008] Sydansk even further notes that at that time, a process is neededfor hydraulically fracturing a subterranean hydrocarbon-bearingformation with a stable homogeneous viscous fracturing fluid havingsatisfactory performance properties to meet the demands of the fracturetreatment.

[0009] As a solution to the deficiencies and needs of the prior art,Sydansk, discloses the use of a water soluble carboxylate crosslinkingpolymer along with a chromic carboxylate complex crosslinking agent as alost circulation material.

[0010] While U.S. Pat. No. 5,377,760, issued Jan. 3, 1995 to Merrilldiscloses addition of fibers to an aqueous solution of partiallyhydrolyzed polyacrylamide polymer, with subsequent injection into thesubterranean to improve conformance, the requirements of a hydraulicfracturing fluid are so different from a conformance fluid, that suchwould not necessarily work for hydraulic fracturing treatment.

[0011] Additionally, Merrill's conformance treatment method of mixingthe fibers with the polymer solution followed by injection, requires amultiplicity of storage and mixing tanks, and a metering system whichmust be operated during the operation of the well. Specifically, a firsttank will store a water and polymer solution, a second tank will store awater and cross-linking solution, and a third tank will be used to mixfibers with polymer solution from the first tank to create apolymer/fiber slurry. This polymer/fiber slurry is then metered from thethird tank and combined with cross-linking solution metered from thesecond tank to the well bore.

[0012] As an advance over the above prior art, U.S. Pat. No. 6,016,871,issued Jan. 25, 2000, to Boyce D. Burts, Jr., for “Hydraulic fracturingadditive, hydraulic fracturing treatment fluid made therefrom, andmethod of hydraulically fracturing a subterranean formation,” disclosesan additive including a dry mixture of water soluble crosslinkablepolymer, a crosslinking agent, and a reinforcing material of fibersand/or comminuted plant materials. The method of forming a fluidincludes contacting the additive with water or an aqueous solution, witha method of treating the formation further including the step ofinjecting the fluid into the formation.

[0013] While not believed to be related prior art because they relate todifferent types of well operations, for completeness, attention isdirected to five other similar “dry mixture” patents by Boyce D. Burts,Jr., which were filed on the same day (Oct. 31, 1997) as the '871patent: U.S. Pat. No. 6,218,343, issued Apr. 17, 2001, for “Additivefor, treatment fluid for, and method of plugging a tubing/casing annulusin a well bore,” U.S. Pat. No. 6,102,121, issued Aug. 15, 2000, for“Conformance improvement additive, conformance treatment fluid madetherefrom, method of improving conformance in a subterranean formation,”U.S. Pat. No. 6,098,712, issued Aug. 8, 2000, for “Method of plugging awell,” U.S. Pat. No. 6,016,879, issued Jan. 25, 2000, for “Lostcirculation additive, lost circulation treatment fluid made therefrom,and method of minimizing lost circulation in a subterranean formation,”and U.S. Pat. No. 6,016,869, issued Jan. 25, 2000, for “Well killadditive, well kill treatment fluid made therefrom, and method ofkilling a well.”

[0014] A number of patents discuss the use of diatomaceous earth (“DE”)in a well operation.

[0015] U.S. Pat. No. 3,380,542, issued Apr. 30, 1968 to Clear, forrestoring lost circulation discloses a oil-based drilling fluid,containing a slurry of diatomite and asbestos, used to restore lostcirculation during well drilling operations.

[0016] U.S. Pat. No. 4,369,844, issued Jan. 25, 1983 to Clear, disclosesthat various formation sealing agents have been used in the art to formformation seals and/or filter cakes on the wall of a well bore,including diatomaceous earth.

[0017] U.S. Pat. No. 4,110,225, issued Aug. 29, 1978 to Cagle, disclosesthat zones of lost circulation and other undesired fluid communicationchannels into a wellbore are sealed by isolating a volume in the wellincluding such a zone and applying greater than formation pressure to anovel slurry spotted in the zone until it hardens into a solid,drillable seal. The slurry contains per barrel from 5-50 poundsdiatomaceous mix, from about 35 to about 350 pounds of oil well cement,and at a minimum about 5 to 6 pounds of a flake type lost-circulationagent. This '225 patent cites a number of patents that disclosecement/diatomaceous earth compositions, including U.S. Pat. Nos.2,585,336; 2,793,957; 2,961,044; 3,467,198; and 3,558,335.

[0018] Regarding these patents, the '225 patent notes the following:

[0019] Regarding U.S. Pat. No. 2,585,336, the '225 patent notes, “amixture is made using from 2% to 100% diatomaceous earth, compared tothe content of the cement in the slurry. The aim of the inventors was toprevent perlite from settling and to produce a lightweight cement. Thediatomaceous earth-cement described in the disclosure is a mixture ofPortland cement, perlite and diatomaceous earth, lime, and asbestosfibers.”

[0020] Regarding U.S. Pat. No. 2,793,957, the '225 patent notes, “refersto a highly permeable cement formed by use of the same basic mixtures ofdiatomaceous earth with Portland cement, the diatomaceous earth presentbeing from five to seven times the proportion of the Portland cement inthe slurry. The aim of the inventors was to produce a light highlypermeable cement, entirely opposite to the purpose of my invention.”

[0021] Regarding U.S. Pat. No. 2,961,044, the '225 patent notes,“discusses and claims a cement composition which has diatomaceous earthin the amounts of from 30% to 70% of the Portland cement. The reason forusing the diatomaceous earth was to prevent the strength retrogressionof a salt-saturated cement. Thus, while Shell wishes (among other uses)to employ his mixture for squeeze cementing, he produces a relativelyhigh-strength cement plug. There is a real tendency when redrilling sucha plug for the bit to be deflected or sidetracked so that the new holeis beside rather than through the bore and the seal is ineffective. Thisis completely different from my invention which minimizes such tendencyby producing a plug at least as drillable as the formation in which itis set. Also, Shell is directed to operations using salt-saturatedcement slurries, while I prefer using a fresh or brackish water slurry.I employ lost-circulation agents; he makes no teaching of using suchadditives. Accordingly, his teaching is quite far from mine.”

[0022] Regarding both U.S. Pat. Nos. 3,467,198 and 3,558,335, the '225patent notes, “describe cement compositions having diatomaceous mixpresent in the amounts from 0.5% to 10% of the amount of Portland cementpresent to prevent solids-settling.”

[0023] U.S. Pat. No. 4,369,844, issued Jan. 25, 1983 to Clear, disclosesslurries to seal permeable earth formations encountered in the drillingof wells, comprising finely divided paper, diatomaceous earth, and in afurther embodiment, lime. A slug of the slurry is spotted at the locusof the permeable formation and defluidized to form a formation seal onwhich a mud sheath is then deposited.

[0024] U.S. Pat. No. 4,505,751, issued Mar. 19, 1985, discloses asilicate/silica cement in oil field applications, including diatomaceousearth as a species of silica compound.

[0025] While not believed to be analogous prior art because it relatesto earthen pits (for example a ditch) and not to subterrean wellboresnor well operations, U.S. Pat. No. 5,947,644, issued Sep. 7, 1999 toGibbons et al., is included herein for completeness because it disclosesa gelable slurry of aqueous solvent, a crosslinkable polymer, acrosslinking agent, and unconsolidated solids such as diatomaceousearth. This gelable slurry is placed in an earthen pit and allowed toform into a fluid impermeable barrier wall in the earthen pit. Thepolymer serves to bind the unconsolidated solids to convert the gelableslurry to a nondeformable gelled continuum of consolidated solids, whichforms the barrier wall in the earthen pit. As disclosed in the '644patent in the Summary of the Invention section, at col. 1, lines 57-67,this gelable slurry is prepared by first forming a liquid gelationsolution of the polymer and crosslinking agent, to which is subsequentlymixed with the unconsolidated solids, or alternatively, by sequentiallymixing the aqueous solvent, crosslinkable polymer, and polymercrosslinking agent with the unconsolidated solids.

[0026] Thus, in spite of the advancements in the prior art, there stillneed for further innovation in the hydraulic fracturing additives.

[0027] There is need for further innovation for hydraulic fracturingadditives utilizing a water soluble polymer.

[0028] There is another need for a hydraulic fracturing additive whichwould allow for simplification of the mixing equipment.

[0029] These and other needs in the art will become apparent to those ofskill in the art upon review of this specification, including itsdrawings and claims.

SUMMARY OF THE INVENTION

[0030] It is an object of the present invention to provide for furtherinnovation in hydraulic fracturing additives.

[0031] It is an another object of the present invention to provide forfurther innovation for hydraulic fracturing additives utilizing a watersoluble polymer.

[0032] It is even another object of the present invention to provide fora hydraulic fracturing additive which would allow for simplification ofthe mixing equipment.

[0033] These and other objects of the present invention will becomeapparent to those of skill in the art upon review of this specification,including its drawings and claims.

[0034] According to one embodiment of the present invention, there isprovided a hydraulic fracturing additive comprising a dry mixture ofwater soluble crosslinkable polymer, a crosslinking agent, and a filteraid.

[0035] According to another embodiment of the present invention, thereis provided a well fluid comprising a hydraulic fracturing fluid, watersoluble crosslinkable polymer, a crosslinking agent, and a filter aid.

[0036] According to even another embodiment of the present invention,there is provided a method of modifying a hydraulic fracturing fluid.The method includes contacting the hydraulic fracturing fluid with awater soluble crosslinkable polymer, crosslinking agent, and filter aidto form a modified hydraulic fracturing fluid.

[0037] According to still another embodiment of the present invention,there is provided a method for hydraulically fracturing a subterraneanhydrocarbon bearing formation below an earthen surface in fluidcommunication with a wellbore. The method includes providing a hydraulicfracturing fluid comprising water soluble crosslinkable polymer, acrosslinking agent, and filter aid. The method also includes injectingthe hydraulic fracturing fluid into said formation via said wellbore ata pressure sufficient to hydraulically fracture said formation.

[0038] According to yet another embodiment of the present invention,there is provided a method for hydraulically fracturing a subterraneanhydrocarbon bearing formation below an earthen surface in fluidcommunication with a wellbore. The method includes providing a hydraulicfracturing additive comprising a dry mixture of water solublecrosslinkable polymer, a crosslinking agent, and filter aid. The methodalso includes contacting the hydraulic fracturing additive with water oran aqueous solution to form a hydraulic fracturing fluid. The methodalso includes injecting the hydraulic fracturing fluid into saidformation via said wellbore at a pressure sufficient to hydraulicallyfracture said formation.

[0039] According to even still another embodiment of the presentinvention, there is provided a method of circulating a hydraulicfracturing fluid in a welbore penetrating a subterranean formation. Themethod includes providing a hydraulic fracturing fluid comprising wateror an aqueous solution, water soluble crosslinkable polymer, acrosslinking agent, and a filter aid. The method also includescirculating the hydraulic fracturing fluid in the wellbore.

[0040] According to even yet another embodiment of the presentinvention, there is provided a method of modifying a hydraulicfracturing fluid circulating in a wellbore penetrating a subterraneanformation. The method includes introducing a water soluble crosslinkablepolymer, crosslinking agent, and filter aid to the circulating hydraulicfracturing fluid.

[0041] Various further embodiments of any or all of the aboveembodiments include any or all of the following in any combination: thefilter aid is selected from the group consisting of diatomaceous earth,perlite, glass beads, magnesium silicate, solid thermoplastic orthermoset polymer beads, talc, and calcium silicate; or the polymer isan a carboxylate-containing polymer, and the crosslinking agent isselected from the group consisting of chromium (III) carboxylatecomplexes, aldehydes, dialdehydes, formaldehydes, glutaraldehyde,dichromates, titanium chelates, phenols, substituted phenols, ethers,aluminum citrate, and aluminates; the filter aid comprises at least oneof diatomaceous earth or pearlite; the polymer comprises a low molecularweight polymer having a molecular weight less than 500,000, and a highmolecular weight polymer having a molecular weight of at least 500,000;the polymer is a water soluble, carboxylate containing acrylamide, andthe crosslinking agent is a chromium (III) carboxylate complex; thefilter aid is diatomaceous earth; the filter aid is pearlite; thereinforcing material selected from the group consisting of hydrophilicfibers, hydrophobic fibers, and comminuted plant material; and/orvarious weight percentages are in the range of about 4 to about 35weight percent polymer, in the range of about 1 to about 10 weightpercent cross linking agent, and in the range of about 55 to about 95weight percent filter aid, based on the total weight of the polymer,cross linking agent and filter aid.

[0042] These and other embodiments of the present invention will becomeapparent to those of skill in the art upon review of this specificationand claims.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The hydraulic fracturing additive of the present inventionincludes polymer, cross-linking agent, filter aid, and optionally areinforcing material, preferably either fibers or comminuted particlesof plant materials, and optionally any other materials that are known inthe art. It is to be understood that the hydraulic fracturing additiveof the present invention may be in the form of a dry mixture or aslurry. In a preferred embodiment of the present invention, thehydraulic fracturing additive is a dry mixture.

[0044] A well fluid of the present invention includes well fluidcomponents plus the additive of the present invention, and optionallyconventional proppants as are known in the art.

[0045] Any suitable relative amounts of the polymer, cross-linkingagent, filter aid and the optional reinforcing materials may be utilizedin the present invention provided that the desired hydraulic fracturingresults are achieved. Generally, the relative amounts of each will bedetermined based on the particular application to which the additive isto be subjected. A suitable amount of crosslinking agent is provided toreach the desired amount of crosslinking. The amount of reinforcingmaterial is selected to provide desired physical properties.

[0046] Any suitable types of filter aid materials as are known in thefiltration art may be utilized as the filter aid component in thepresent invention. All that is necessary is that the filter aid willfunction to be “squeezed” and allow migration of the solution of polymerand crosslinking agent into the formation, and will form a plug of thefilter aid that will hold the solution in place until it sufficientlycrosslinks. Non-limiting examples of which include diatomaceous earth(“DE” or diatomite), perlite (or pearlite), glass beads, magnesiumsilicate, solid thermoplastic or thermoset polymers generally in powderform, talc (naturally occuring form of hydrous magnesium silicatecontaining varying proportions of such associated minerals asalpha-quartz, calcite, chlorite, dolomite, kaolin, magnesite, andphlogopite), and calcium silicate (for example, see, U.S. Pat. No.5,750,038, issued May 12, 1998, to Tsunematsu, for “Method for thepreparation of acid-resistant calcium silicate,” incorporate herein byreference). Preferably, the filter aid is selected from the groupconsisting of diatomaceous earth perlite (or pearlite), magnesiumsilicate, and talc. More preferably, the filter aid is a mineral basedtype of filter aid, non-limiting examples of which include diatomaceousearth, pearlite, magnesium silicate, talc and calcium silicate. Evenmore preferably, the filter aid comprises pearlite and/or diatomaceousearth. Still more preferably, the filter aid comprises diatomaceousearth.

[0047] The amount of filter aid to be utilized is generally notdependent upon the amount of polymer or crosslinking agent, but rather,is that amount sufficient to form a plug to retain the polymer in placeuntil it crosslinks sufficiently to remain in place on its own. However,in an effort to quantify the amount of filter aid, a weight ratio offilter aid to polymer is provided for convenience.

[0048] Generally, the weight ratio of filter aid:polymer in the additiveis in the range of about 100:1 to about 1:100, preferably in the rangeof about 50:1 to about 1:50, more preferably in the range of about 15:1to about 1:15, even more preferably in the range of about 5:1 to about1:5, and still more preferably in the range of about 5:1 to about 1:1.

[0049] Commercially, it is envisioned that the additive will be packagedin a single bag, to promote ease of use and eliminate the necessity ofany measuring and/or mixing at the well site. As a non-limiting exampleof a commercial embodiment, a 40 pound bag might contain any where fromabout 1.5 to about 17.5 lbs. polymer, from about 0.4 to about 5 lbs.crosslinking agent, and the balance of from about 17.5 to about 38.1lbs. filter aid.

[0050] In weight percentage terms, examples of weight percentage rangesinclude from about 4 to about 35 weight percent polymer, from about 1 toabout 10 weight percent cross linking agent, and from about 55 to about95 weight percent filter aid, based on the total weight of the polymer,cross linking agent and filter aid. Specific non-limiting examples ofuseful compositions include 4% polymer, 1% cross linker, 95% DE, or 24%polymer, 6% cross linker, 70% DE, or 35% polymer, 10% cross linker, 55%DE.

[0051] The particle size distribution of the filter aid is selected toallow dewatering of the filter aid (i.e., the solution containingpolymer and crosslinking agent will separate from the filter aid), andto allow formation of a plug of the filter aid that retains the polymerand crosslinking agent in the reservoir during crosslinking. It isbelieved that the particle size distribution will be determined by thereservoir conditions.

[0052] Other additives as are known in the well fluid art may beutilized, non limiting examples of which include surfactants,dispersants, retarders, accelerants, weighting agents (such as hematite,barite or calcium carbonate), lost circulation materials and otheradditives may be provided as necessary or desired.

[0053] The polymer utilized in the practice of the present invention ispreferably water soluble and must be capable of being pumped as a liquidand subsequently crosslinked in place to form a substantiallynon-flowing crosslinked polymer which has sufficient strength towithstand the pressures exerted on it. Moreover, it must have a networkstructure capable of incorporating reinforcing fibers.

[0054] The crosslinked polymer or “gel” resulting from the crosslinkedpolymer system of the present invention is a continuousthree-dimensional crosslinked polymeric network, having an ultra highmolecular weight, which confines the aqueous solvent component in itsinterstices. The polymeric network and aqueous component form a singlephase system which provides the gel with its unique phase behavior.

[0055] The present gel is qualitatively defined as “flowing” because ofits ability to flow into the wellbore and formation under injectionpressure. Nevertheless, the gel has sufficient structure as a result ofits specific crosslinking mechanism to exhibit characteristics desirableof a fracturing fluid. These characteristics include uniformity, highviscosity, shear thinning and stability during the fracture treatment aswell as low fluid loss and friction loss.

[0056] The uniform viscous stable gel of the present invention is aparticularly effective vehicle for propping agents, which may beemployed during the fracture treatment, because the gel isadvantageously susceptible to shear thinning. The gel exhibits highapparent viscosity in the wellbore tubulars during injection, butexhibits relatively low apparent viscosity when subjected to high shearas it exits the wellbore perforations and enters the induced fractures.The gel regains its high apparent viscosity as it moves at lower shearthrough the fractures far into the formation away from the wellbore. Theshear thinning gel effectively maintains the proppant in suspension inthe wellbore tubulars until the gel enters the induced fractures andagain after the gel has traveled into the fractures.

[0057] The gel of the present invention is at least partially gelledupon injection into the wellbore. In a partial gel, as defined herein,the crosslinking agent has reacted incompletely with the polymer andneither all of the polymer nor all of the crosslinking agent in the gelis totally consumed by the crosslinking reaction. Although the partialgel exhibits at least some gel-like structure, it is capable of furthercrosslinking to completion without the addition of more crosslinkingagent.

[0058] “Crosslinked to completion” means that the gel is substantiallyincapable of further crosslinking because one or both of the requiredreactants in the initial solution are substantially consumed. Furthercrosslinking is only possible if either polymer, crosslinking agent, orboth are added to the gel. In a preferred embodiment, the gel of thepresent invention is crosslinked to substantial completion uponinjection into the wellbore.

[0059] Complete gelation by the time the gel reaches the inducedfractures is advantageous because it promotes efficient proppanttransport and reduces fluid loss. Fluid loss can cause significantpermeability reduction of the matrix bounding the fracture network whichis counterproductive to the fracturing process. Fluid loss can alsoincrease the fracturing fluid requirement of the treatment and causeundesirable proppant bridging in the fractures.

[0060] The polymer utilized in the practice of the present invention ispreferably water soluble and must be capable of being pumped as a liquidand subsequently crosslinked in place to form a substantiallynon-flowing crosslinked polymer which has sufficient strength towithstand the pressures exerted on it. optionally, when reinforcingmaterials are utilized, it would have a network structure capable ofincorporating reinforcing materials.

[0061] While any suitable water soluble polymer may be utilized, thepreferred polymer utilized in the practice of the present invention is awater soluble carboxylate-containing polymer, more preferably a watersoluble partially hydrolyzed carboxylate-containing polymer. Thiscarboxylate-containing polymer may be any crosslinkable, high molecularweight, water-soluble, synthetic polymer or biopolymer containing one ormore carboxylate species.

[0062] For an example of polymers and crosslinking agents suitable foruse herein and details regarding their making and use, please see any ofthe above listed patents to Boyce D. Burts, Jr. all herein incorporatedby reference, or please see U.S. Pat. Nos. 4,683,949, 4,723,605,4,744,418, 4,770,245, 4,844,168, 4,947,935, 4,957,166 and 4,989,673,5,377,760, 5,415,229, 5,421,411, all herein incorporated by reference.

[0063] The average molecular weight of the carboxylate-containingpolymer utilized in the practice of the present invention is in therange of about 10,000 to about 50,000,000, preferably in the range ofabout 100,000 to about 20,000,000, more preferably in the range of about200,000 to about 15,000,000, and still more preferably in the range ofabout 200,000 to about 10,000,000.

[0064] In some instances, a blend of two polymers, a lower molecularweight polymer and a higher molecular weight polymer may be utilized.For example, in some instances where high fluid loss is encountered,such as a hole in the casing, a fault zone, loose sand, unconsolidatedzones, or vugular formations, higher molecular weight polymer must beutilized. However, this higher molecular weight polymer causes problemsin mixing, pumping and total polymer load. Thus, this higher molecularweight polymer is mixed with a lower molecular weight polymer to providemixing, pumping and loading as desired.

[0065] Generally, this lower molecular weight polymer has a molecularweight less than 1,000,000, preferably less than 500,000, and morepreferably less than 200,000. Generally the lower molecular weightpolymer will have a molecular weight in the range of about 20,000 toless than 1,000,000, preferably in the range of about 20,000 to lessthan 500,000, and more preferably in the range of about 200,000 to lessthan 500,000. The higher molecular weight polymer generally has amolecular weight of at least 1,000,000, preferably from about 1,000,000to about 50,000,000, more preferably from about 5,000,000 to about20,000,000, and even more preferably from about 6,000,000 to about12,000,000.

[0066] Biopolymers useful in the present invention includepolysaccharides and modified polysaccharides. Non-limiting examples ofbiopolymers are xanthan gum, guar gum, carboxymethylcellulose,o-carboxychitosans, hydroxyethylcellulose, hydroxypropylcellulose, andmodified starches. Non-limiting examples of useful synthetic polymersinclude acrylamide polymers, such as polyacrylamide, partiallyhydrolyzed polyacrylamide and terpolymers containing acrylamide,acrylate, and a third species. As defined herein, polyacrylamide (PA) isan acrylamide polymer having substantially less than 1% of theacrylamide groups in the form of carboxylate groups. Partiallyhydrolyzed polyacrylamide (PHPA) is an acrylamide polymer having atleast 1%, but not 100%, of the acrylamide groups in the form ofcarboxylate groups. The acrylamide polymer may be prepared according toany conventional method known in the art, but preferably has thespecific properties of acrylamide polymer prepared according to themethod disclosed by U.S. Pat. No. Re. 32,114 to Argabright et alincorporated herein by reference.

[0067] Any crosslinking agent suitable for use with the selected polymermay be utilized in the practice of the present invention. Non limitingexamples of suitable crosslinking agents includes chromium (III)carboxylate complexes, aldehydes, dialdehydes, formaldehydes,glutaraldehyde, dichromates, titanium chelates, phenols, substitutedphenols, ethers, aluminum citrate, and aluminates.

[0068] Preferably, the crosslinking agent utilized in the presentinvention is a chromic carboxylate complex.

[0069] The term “complex” is defined herein as an ion or moleculecontaining two or more interassociated ionic, radical or molecularspecies. A complex ion as a whole has a distinct electrical charge whilea complex molecule is electrically neutral. The term “chromiccarboxylate complex” encompasses a single complex, mixtures of complexescontaining the same carboxylate species, and mixtures of complexescontaining differing carboxylate species.

[0070] The chromic carboxylate complex useful in the practice of thepresent invention includes at least one or more electropositive chromiumIII species and one or more electronegative carboxylate species. Thecomplex may advantageously also contain one or more electronegativehydroxide and/or oxygen species. It is believed that, when two or morechromium III species are present in the complex, the oxygen or hydroxidespecies may help to bridge the chromium III species. Each complexoptionally contains additional species which are not essential to thepolymer crosslinking function of the complex. For example, inorganicmono- and/or divalent ions, which function merely to balance theelectrical charge of the complex, or one or more water molecules may beassociated with each complex. Non-limiting representative formulae ofsuch complexes include:

[Cr₃(CH₃CO₂)₆(OH)₂]¹⁺;

[Cr₃(CH₃CO₂)₆(OH)₂]NO₃.6H₂O;

[Cr₃(CH₃CO₂)₆(OH)₂]³⁺; and

[Cr₃(CH₃CO₂)₆(OH)₂](CH₃CO₂)₃.H₂O.

[0071] “Trivalent chromium” and “chromic ion” are equivalent termsencompassed by the term “chromium III” species as used herein.

[0072] The carboxylate species are advantageously derived fromwater-soluble salts of carboxylic acids, especially low molecular weightmono-basic acids. Carboxylate species derived from salts of formic,acetic, propionic, and lactic acid, substituted derivatives thereof andmixtures thereof are preferred. The preferred darboxylate speciesinclude the following water-soluble species: formate, acetate,propionate, lactate, substituted derivatives thereof, and mixturesthereof. Acetate is the most preferred carboxylate species. Examples ofoptional inorganic ions include sodium, sulfate, nitrate and chlorideions.

[0073] A host of complexes of the type described above and their methodof preparation are well known in the leather tanning art. Thesecomplexes are described in Shuttleworth and Russel, Journal of theSociety of Leather Trades' Chemists, “The Kinetics of Chrome TannagePart I.,” United Kingdom, 1965, v. 49, p. 133-154; “Part III.,” UnitedKingdom, 1965, v. 49, p. 251-260; “Part IV.,” United Kingdom, 1965, v.49, p. 261-268; and Von Erdman, Das Leder, “Condensation of MononuclearChromium (III) Salts to Polynuclear Compounds,” Eduard Roether Verlag,Darmstadt Germany, 1963, v. 14, p. 249; and incorporated herein byreference. Udy, Marvin J., Chromium. Volume 1: Chemistry of Chromium andits Compounds. Reinhold Publishing Corp., N.Y., 1956, pp. 229-233; andCotton and Wilkinson, Advanced Inorganic Chemistry 3rd Ed., John Wileyand Sons, Inc., N.Y., 1972, pp. 836-839, further describe typicalcomplexes which may be within the scope of the present invention and areincorporated herein by reference. The present invention is not limitedto the specific complexes and mixtures thereof described in thereferences, but may include others satisfying the above-stateddefinition.

[0074] Salts of chromium and an inorganic monovalent anion, e.g., CrCl3,may also be combined with the crosslinking agent complex to accelerategelation of the polymer solution, as described in U.S. Pat. No.4,723,605 to Sydansk, which is incorporated herein by reference.

[0075] The molar ratio of carboxylate species to chromium III in thechromic carboxylate complexes used in the process of the presentinvention is typically in the range of 1:1 to 3.9:1. The preferred ratiois range of 2:1 to 3.9:1 and the most preferred ratio is 2.5:1 to 3.5:1.

[0076] The optional reinforcing material of the present invention maycomprise fibers or comminuted particles of plant materials, andpreferably comprises comminuted particles of one or more plantmaterials.

[0077] Fibers suitable for use in the present invention are selectedfrom among hydrophilic and hydrophobic fibers. Incorporation ofhydrophobic fibers will require use of a suitable wetting agent.Preferably, the fibers utilized in the present invention comprisehydrophilic fibers, most preferably both hydrophilic and hydrophobicfibers.

[0078] With respect to any particular fiber employed in the practice ofthe present invention, it is believed that the longer the fiber, themore difficult it is to be mixed uniformly in solution. It is believedthat fibers as long as 12,500 microns may tend to aggregate and formclumps. The shorter the fiber, it is believed the easier it is to mix insolution. On the other hand, the shorter the fiber, the greater thequantity necessary to provide the desired level of strength in areinforced mature gel. In general, the fibers utilized in the presentinvention will have a length in the range of 100 microns to 3200microns, preferable 100 microns to 1000 microns.

[0079] Non-limiting examples of suitable hydrophobic fibers includenylon, rayon, hydrocarbon fibers and mixtures thereof.

[0080] Non-limiting examples of suitable hydrophilic fibers includeglass, cellulose, carbon, silicon, graphite, calcined petroleum coke,cotton fibers, and mixtures thereof.

[0081] Non-limiting examples of comminuted particles of plant materialssuitable for use in the present invention include any derived from: nutand seed shells or hulls such as those of peanut, almond, brazil, cocoabean, coconut, cotton, flax, grass, linseed, maize, millet, oat, peach,peanut, rice, rye, soybean, sunflower, walnut, wheat; various portionsof rice including the rice tips, rice straw and rice bran; crude pectatepulp; peat moss fibers; flax; cotton; cotton linters; wool; sugar cane;paper; bagasse; bamboo; corn stalks; various tree portions includingsawdust, wood or bark; straw; cork; dehydrated vegetable matter(suitably dehydrated carbonhydrates such as citrus pulp, oatmeal,tapioca, rice grains, potatoes, carrots, beets, and various grainsorghams); whole ground corn cobs; or various plant portions the corncob light density pith core, the corn cob ground woody ring portion, thecorn cob coarse or fine chaff portion, cotton seed stems, flax stems,wheat stems, sunflower seed stems, soybean stems, maize stems, rye grassstems, millet stems, and various mixtures of these materials.

[0082] Optionally a dispersant for the comminuted plant material in therange of about 1 to about 20 pounds, preferably in the range of about 5to about 10 pounds, and more preferably in the range of about 7 to about8 pounds of dispersant may be utilized per pound of comminuted plantmaterial. A non-limiting example of a dispersant would be NaCl.

[0083] Preferred comminuted materials useful in the practice of thepresent invention include those derived from peanuts, wood, paper anyportion of rice seed or plant, and any portion of corn cobs.

[0084] These various materials can be comminuted to very fine particlesizes by drying the products and using hammer mills, cutter heads, aircontrol mills or other comminution methods as is well known to those ofskill in the comminution art. Air classification equipment or othermeans can be used for separation of desired ranges of particle sizesusing techniques well-known in the comminution art.

[0085] Any suitable size of comminuted material may be utilized in thepresent invention, along as such size produces results which aredesired. Of course, the particle size will be a function of diameter ofthe porosity passages. While the present invention will find utility forpassages on the order of microns in diameter, it will also find utilityon larger passages, for example, those with diameters greater than{fraction (1/64)}, {fraction (1/16)} or event ⅛ of an inch.

[0086] In most instances, the size range of the comminuted materialsutilized herein will range from below about 8 mesh (“mesh” as usedherein refers to standard U.S. mesh), preferably from about −65 mesh toabout −100 mesh, and more preferably from about −65 mesh to about −85mesh. Specifically preferred particle sizes for some materials areprovided below.

[0087] Preferred mixtures of comminuted materials useful in the practiceof the present invention include a rice fraction and peanut hulls; arice fraction and wood fiber and/or almond hulls; a rice fraction and acorn cob fraction, preferably a chaff portion; and a corn cob fraction,preferably a pith or chaff portion, a rice fraction, and at least one ofwood fiber, nut shells, paper and shredded cellophane.

[0088] Rice is commercially available in the form of rice hulls, ricetips, rice straw and rice bran, as these various parts of the rice plantare separated commercially and are widely available from rice mills.Preferably, the size range of the rice fraction utilized herein willrange from below about 8 mesh (“mesh” as used herein refers to standardU.S. mesh) , preferably from about −65 mesh to about −100 mesh, and morepreferably from about −65 mesh to about −85 mesh.

[0089] After the corn kernals are removed, corn cobs consist of fourprinciple parts that are arranged concentrically. The central portion isa very light density pith core, that is surrounded by a woody ring, thatin turn is surrounded by a coarse chaff portion, that in turn is coveredby a fine chaff portion. The coarse and fine chaff portions form thesockets for ancoring the corn kernels to the corncob. The normal methodsof grinding corncobs produce a mixture of all four parts enumeratedabove. It is possible, however, to separate the woody ring material fromthe remainder of the cob. The chaff portion of the corncob remainingafter removal of the woody ring material is known as “bees wings”. Inthe present invention, any of the pith or chaff portions(“BPC”) are thepreferred portions of the corn cob, with the chaff portions being morepreferred. A range of particle sizes of pith and chaff can be obtainedfrom comminution, but the size range smaller than about 8 mesh issuitable for this invention. Preferably, a particle size distributionranging from smaller than 8 mesh to smaller than 100 mesh is utilized.

[0090] Preferred woods for use as comminuted materials in the presentinvention include any type of hard wood fiber, including cedar fiber,oak fiber, pecan fiber and elm fiber. Preferably the wood fibercomprises cedar fibers.

[0091] Preferred nut shells for use in the present invention includepecan, walnut, and almond. Preferably, the nut shells comprise at leastone of pecan or walnut shells.

[0092] Preferred particle sizes for the wood fibers, nut shells, paperand cellophane will generally range from about +10 mesh to −100 mesh. Anillustration of a non-limiting particle size distribution for thesematerials would include particles of +10 mesh, +20 mesh, +30 mesh, +50mesh, +60 mesh, +100 mesh, and −100 mesh.

[0093] For one of the preferred comminuted plant mixtures comprising acorn cob fraction, a rice fraction, and at least one of wood fiber, nutshells, paper and shredded cellophane, the mixture will generallycomprise in the range of about 5 to about 95 weight percent rice, in therange of about 5 to about 95 weight percent corncob pith or chaff, withthe total of ground wood fiber, ground nut shells, ground paper andshredded cellophane comprising in the range of about 5 to about 95weight percent (weight percent based on the total weight of plantmaterial in the mixture. Preferred ranges are about 20 to about 75weight percent rice, about 5 to about 35 weight percent corncob pith orchaff, with the total of ground wood fiber, ground nut shells, groundpaper and shredded cellophane comprising in the range of about 20 toabout 75 weight percent. More preferred ranges are about 30 to about 50weight percent rice, about 10 to about 30 weight percent corncob pithand chaff, with the total of ground wood fiber, ground nut shells,ground paper and shredded cellophane comprising in the range of about 25to about 50 weight percent.

[0094] As these comminuted materials are to be added to a water baseconformance fluid, a small amount of oil may optionally added to themixture. This optional oil is preferably added while the plant materialsare being mixed together. This mixing may take place in a ribbonblender, where the oil in the required amount is applied by a spray bar.The oil wets the particles and adds to their lubricity while at the sametime helping to control dust produced by the mixing operation. A varietyof oils may be utilized in the practice of the present invention inconcentrations generally ranging from about 1 percent to about 5 percentby weight based on the total weight of the mixture of comminutedmaterials, more preferably ranging from about 1 percent to about 2percent. A non-limiting example of a commercially available oil suitablefor use in the present invention includes ISOPAR V, available from ExxonCorporation.

[0095] In the method of the present invention for forming a hydraulicfracturing additive, the various components of polymer, crosslinkingagent and filter aid, may be mixed in any form (dry form, liquid form,or slurry form) in any suitable order utilizing mixing techniques asknown to those in the art.

[0096] Specifically, a dry hydraulic fracturing additive may be formedby mixing solid polymer, solid crosslinking agent and solid filter aidto form a solid (dry) hydraulic fracturing additive.

[0097] In the practice of the present invention, liquid hydraulicfracturing additive may be formed by mixing the various components inany form (dry form or liquid or slurry form) in any suitable orderutilizing mixing techniques as know to those in the art. If the variouscomponents are mixed in dry form, this dry mixture may subsequently maybe contacted with water or aqueous solution to form a liquid hydraulicfracturing additive.

[0098] Hydraulic fracturing fluids are known to those of skill in theart, and would generally be of the category of well fluid known asdrilling fluids. Generally such fluids are liquids in which a densityagent has been included to increase the density of the fluid (generallysome type of metal salt), and also may optionally include a solid phase.

[0099] In a method of treating a hydraulic fracturing fluid, thehydraulic fracturing fluid to be treated is contacted with a liquid orsolid form of the hydraulic fracturing additive of the presentinvention. Preferably, the hydraulic fracturing fluid is contacted witha dry mixture (i.e., solid form) of the hydraulic fracturing additive.Of course, the various components of the additive (i.e., polymer,crosslinking agent, and filter aid) may be added individually to thehydraulic fracturing fluid to be treated.

[0100] A well fluid of the present invention comprises an aqueouscomponent, polymer, crosslinking agent, and filter aid. A modifiedhydraulic fracturing fluid comprises a traditional hydraulic fracturingfluid and the hydraulic fracturing additive or fluid of the presentinvention.

[0101] In a method of operating a well of the present invention in whicha well fluid is circulating down from the surface of the well, throughthe drill string positioned in a wellbore, and out through openings inthe drill bit such that the well fluid is then circulated upwardly inthe annulus between the side of the wellbore and the rotating drillstring, the present invention includes circulating such a well fluidcomprising the hydraulic fracturing additive. The hydraulic fracturingadditive can be added to the circulating fluid in liquid or solid formor of course, the individual components may be added to the circulatingfluid in liquid or solid form. Alternatively, the hydraulic fracturingadditive may be added to the fluid prior to it being circulated.

[0102] In well operation, it is also known to define a verticallylimited zone into which a slurry is then pumped and subsequentlysqueezed by application of pressure (either from the formation itself,or by application of pressure to the zone). In a method of performing awell operation of the present invention, the hydraulic fracturing fluidof the present invention is pumped into a desired vertically definedzone in the well, and then “squeezed” to dewater the fluid such that aplug of the filter aid remains behind and the solution of polymer andcrosslinking agent migrates into the formation. The filter aid plugremains in place to prevent or slow down the escape of the solution backinto the well allowing time for the solution to form a gel plug. In thiswell operation, one may start with a well fluid containing the polymer,crosslinking agent and filter aid, or these various components may beintroduced to the well fluid in any combination/or of one or more inliquid or dry form, or as the additive or hydraulic fracturing fluid asdiscussed above.

[0103] The hydraulic fracturing fluid of the present invention mayoptionally include proppants as are known to those of skill in the art,and/or breakers as are known to those of skill in the art.

[0104] Water or an aqueous may be contacted with the additive to formthe hydraulic fracturing fluid. Non-limiting examples of suitableaqueous solutions include deionized water, fresh water or a brine havinga total dissolved solids concentration up to the solubility limit of thesolids in water.

[0105] The breaker is preferably a composition which is sufficientlyreactive to effectively break the gel within about 48 hours after thefracture treatment, yet not so reactive that it significantly diminishesthe performance properties of the gel during the fracture treatment.Suitable breakers include those known in the art. The gel breakerreverses the gel to a less viscous solution upon completion of thefracture treatment. The less viscous solution is readily removed fromthe fractures so that injected or produced fluids may flow into or outof the fractures.

[0106] The propping agent can be any suitable composition known in theart. Conventional propping agents include sand, glass beads, ceramicbeads, cracked walnut shells, etc. The proppant keeps the fractures openwithout substantially blocking fluid flow after the degraded gel isremoved.

[0107] The present process enables a practitioner to prepare afracturing fluid from the above-described components which exhibitseffective predetermined performance properties. Effective performanceproperties include low fluid, low friction loss, high shear thinning,high proppant carrying capacity and a resonable gelation rate.

[0108] With the present invention, one can produce effective fracturingfluids as a function of the gel composition and gelation conditions.Thus, to effect an optimum fracture treatment according to the presentprocess, the practitioner predetermines the performance properties of agel which are required to meet the fracture treatment demands of thegiven formation and thereafter produces a gel having these predeterminedproperties by selecting the gel composition and gelation conditionsaccordingly.

[0109] The present process is applicable to fracture treatments offormations under most conditions and is specific to fracturing aformation which is in fluid communication with an injection orproduction well. The gels are produced in a manner which renders theminsensitive to most extreme formation conditions. The gels can be stableat formation temperatures up to 115° C. and beyond and at any formationpH contemplated. The gels are relatively insensitive to oil field fluidsand the stratigraphy of the rock. The gels can be employed in carbonateand sandstone strata or strata having varying mineralogy.

[0110] Upon completion of the fracturing process, the gels can beremoved from the fractures by producing them back through the wellbore.The gels are preferably degraded to a less viscous solution beforebackflowing. Conventional chemical breakers to degrade the gels areeither incorporated into the gelation solution during its preparation orseparately injected into the treatment region after the fracturetreatment. As an alternative to backflowing, the gels can be degradedand displaced out into the formation away from the treatment region. Inany case, the gels do not substantially reduce the permeability of theformation near the wellbore or the resultant fracture after the fracturetreatment.

EXAMPLES

[0111] The following examples are provided merely to illustrate some butnot all of the embodiments of the present invention, and are notintended to, nor do they, limit the scope of the claims.

[0112] DE

[0113] The DE utilized in this example was that produced by Eagle PicherMinerals, Inc., and sold under the trademark CELATOM® Diatomite ET-905.As measured, the particle size distribution was:

[0114] 8% +200 mesh

[0115] 92% −200 mesh

[0116] Polymer

[0117] The polymers utilized were obtained from Ciba and awater-soluble, crosslinkable, carboxylate-containing acrylamidepolymers, CIBA 254 (MW from 300,000 to less than 500,000) and CIBA 935(MW from 6 to 9 million).

[0118] Crosslinking Agent

[0119] The crosslinking agent was chromium acetate.

[0120] Formulations

[0121] Formulation No. 1

[0122] 17.5 grams 254

[0123] 5 grams CrIII Acetate

[0124] 27.5 grams DE

[0125] Formulation No. 2

[0126] 12 grams 254

[0127] 3 grams CrIII Acetate

[0128] 25 grams DE

[0129] Formulation No. 1

[0130] 5 grams 935

[0131] 3 grams 254

[0132] 1.2 grams CrIII Acetate

[0133] 30.8 grams DE

[0134] Filter Press Test

[0135] This test was run to simulate the dewatering of the DE in asubterranean formation, and subsequent formation of a plug of DE andseparate crosslinked polymer.

[0136] 30 ml. of plain tap water was added to a beaker and subjected tomixing at 10,000 rpm in a Hamilton Beach commercial drink mixer with asolid agitator. To this blending water was added the above formulations(three separate runs). The sample was allowed to blend for 5 minutes at10,000 rpm. After the 5 minutes of blending, this mixture was placedinto the cylinder of a filter press in which substantial dewatering ofthe DE slurry occured without any pressure applied. Subsequently, 80 psiof pressure was applied to further dewater and consolidate the DE.Finally, heat was applied to the filter press to heat the consolidatedDE and liquid run off. Both the filter press cylinder and collected runoff (water soluble crosslinkable polymer and crosslinking agent-novisible DE) were placed into a 160 deg. F. water bath and allowed tocrosslink. Without being limited in theory, applicant believes thatresidual polymer remaining in the DE after dewatering crosslinks andserves to promote the consolidation of the DE. Once crosslinked, thecollected run off for all of the formulations promotes a rigid ringinggel.

[0137] While the illustrative embodiments of the invention have beendescribed with particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present invention,including all features which would be treated as equivalents thereof bythose skilled in the art to which this invention pertains.

I claim:
 1. A hydraulic fracturing additive comprising a dry mixture ofwater soluble crosslinkable polymer, a crosslinking agent, and a filteraid.
 2. The additive of claim 1, wherein the filter aid is selected fromthe group consisting of diatomaceous earth, perlite, glass beads,magnesium silicate, solid thermoplastic or thermoset polymer beads,talc, and calcium silicate.
 3. The additive of claim 2, wherein thepolymer is an a carboxylate-containing polymer, and the crosslinkingagent is selected from the group consisting of chromium (III)carboxylate complexes, aldehydes, dialdehydes, formaldehydes,glutaraldehyde, dichromates, titanium chelates, phenols, substitutedphenols, ethers, aluminum citrate, and aluminates.
 4. The additive ofclaim 3, wherein the filter aid comprises at least one of diatomaceousearth or pearlite.
 5. The additive of claim 4, wherein the polymercomprises a low molecular weight polymer having a molecular weight lessthan 500,000, and a high molecular weight polymer having a molecularweight of at least 500,000.
 6. The additive of claim 4, wherein thepolymer is a water soluble, carboxylate containing acrylamide, and thecrosslinking agent is a chromium (III) carboxylate complex.
 7. Theadditive of claim 6, wherein the filter aid is diatomaceous earth. 8.The additive of claim 6, wherein the filter aid is pearlite.
 9. Theadditive of claim 6, further comprising reinforcing material selectedfrom the group consisting of hydrophilic fibers, hydrophobic fibers, andcomminuted plant material.
 10. A well fluid comprising a hydraulicfracturing fluid, water soluble crosslinkable polymer, a crosslinkingagent, and a filter aid.
 11. The well fluid of claim 10, wherein thefilter aid is selected from the group consisting of diatomaceous earth,perlite, glass beads, magnesium silicate, solid thermoplastic orthermoset polymer beads, talc, and calcium silicate.
 12. The well fluidof claim 11, wherein the polymer is an a carboxylate-containing polymer,and the crosslinking agent is selected from the group consisting ofchromium (III) carboxylate complexes, aldehydes, dialdehydes,formaldehydes, glutaraldehyde, dichromates, titanium chelates, phenols,substituted phenols, ethers, aluminum citrate, and aluminates.
 13. Thewell fluid of claim 12, wherein the filter aid comprises at least one ofdiatomaceous earth or pearlite.
 14. The well fluid of claim 13, whereinthe polymer comprises a low molecular weight polymer having a molecularweight less than 500,000, and a high molecular weight polymer having amolecular weight of at least 500,000.
 15. The well fluid of claim 13,wherein the polymer is a water soluble, carboxylate containingacrylamide, and the crosslinking agent is a chromium (III) carboxylatecomplex.
 16. The well fluid of claim 15, wherein the filter aid isdiatomaceous earth.
 17. The well fluid of claim 15, wherein the filteraid is pearlite.
 18. The well fluid of claim 15, further comprisingreinforcing material selected from the group consisting of hydrophilicfibers, hydrophobic fibers, and comminuted plant material.
 19. A methodof modifying a hydraulic fracturing fluid comprising: (a) contacting thehydraulic fracturing fluid with a water soluble crosslinkable polymer,crosslinking agent, and filter aid to form a modified hydraulicfracturing fluid.
 20. The method of claim 19, wherein the filter aid isselected from the group consisting of diatomaceous earth, perlite, glassbeads, magnesium silicate, solid thermoplastic or thermoset polymerbeads, talc, and calcium silicate.
 21. The method of claim 20, whereinthe polymer is an a carboxylate-containing polymer, and the crosslinkingagent is selected from the group consisting of chromium (III)carboxylate complexes, aldehydes, dialdehydes, formaldehydes,glutaraldehyde, dichromates, titanium chelates, phenols, substitutedphenols, ethers, aluminum citrate, and aluminates.
 22. The method ofclaim 21, wherein the filter aid comprises at least one of diatomaceousearth or pearlite.
 23. The method of claim 22, wherein the polymercomprises a low molecular weight polymer having a molecular weight lessthan 1,000,000, and a high molecular weight polymer having a molecularweight of at least 1,000,000.
 24. The method of claim 22, wherein thepolymer is a water soluble, carboxylate containing acrylamide, and thecrosslinking agent is a chromium (III) carboxylate complex.
 25. Themethod of claim 24, wherein the filter aid is diatomaceous earth. 26.The method of claim 24, wherein the filter aid is pearlite.
 27. Themethod of claim 19, wherein the water soluble crosslinkable polymer,crosslinking agent, and filter aid, are all in solid form.
 28. A methodfor hydraulically fracturing a subterranean hydrocarbon bearingformation below an earthen surface in fluid communication with awellbore comprising: (a) providing a hydraulic fracturing fluidcomprising water soluble crosslinkable polymer, a crosslinking agent,and filter aid; and (b) injecting the hydraulic fracturing fluid intosaid formation via said wellbore at a pressure sufficient tohydraulically fracture said formation.
 29. The method of claim 28,wherein the filter aid is selected from the group consisting ofdiatomaceous earth, perlite, glass beads, magnesium silicate, solidthermoplastic or thermoset polymer beads, talc, and calcium silicate.30. The method of claim 29, wherein the polymer is an acarboxylate-containing polymer, and the crosslinking agent is selectedfrom the group consisting of chromium (III) carboxylate complexes,aldehydes, dialdehydes, formaldehydes, glutaraldehyde, dichromates,titanium chelates, phenols, substituted phenols, ethers, aluminumcitrate, and aluminates.
 31. The method of claim 30, wherein the filteraid comprises at least one of diatomaceous earth or pearlite.
 32. Themethod of claim 31, wherein the polymer comprises a low molecular weightpolymer having a molecular weight less than 500,000, and a highmolecular weight polymer having a molecular weight of at least 500,000.33. The method of claim 31, wherein the polymer is a water soluble,carboxylate containing acrylamide, and the crosslinking agent is achromium (III) carboxylate complex.
 34. The method of claim 33, whereinthe filter aid is diatomaceous earth.
 35. The method of claim 33,wherein the filter aid is pearlite.
 36. The method of claim 33, furthercomprising reinforcing material selected from the group consisting ofhydrophilic fibers, hydrophobic fibers, and comminuted plant material.37. A method for hydraulically fracturing a subterranean hydrocarbonbearing formation below an earthen surface in fluid communication with awellbore comprising: (a) providing a hydraulic fracturing additivecomprising a dry mixture of water soluble crosslinkable polymer, acrosslinking agent, and filter aid; (b) contacting the hydraulicfracturing additive with water or an aqueous solution to form ahydraulic fracturing fluid; and (c) injecting the hydraulic fracturingfluid into said formation via said wellbore at a pressure sufficient tohydraulically fracture said formation.
 38. The method of claim 37,wherein the filter aid is selected from the group consisting ofdiatomaceous earth, perlite, glass beads, magnesium silicate, solidthermoplastic or thermoset polymer beads, talc, and calcium silicate.39. The method of claim 38, wherein the polymer is an acarboxylate-containing polymer, and the crosslinking agent is selectedfrom the group consisting of chromium (III) carboxylate complexes,aldehydes, dialdehydes, formaldehydes, glutaraldehyde, dichromates,titanium chelates, phenols, substituted phenols, ethers, aluminumcitrate, and aluminates.
 40. The method of claim 39, wherein the filteraid comprises at least one of diatomaceous earth or pearlite.
 41. Themethod of claim 40, wherein the polymer comprises a low molecular weightpolymer having a molecular weight less than 500,000, and a highmolecular weight polymer having a molecular weight of at least 500,000.42. The method of claim 40, wherein the polymer is a water soluble,carboxylate containing acrylamide, and the crosslinking agent is achromium (III) carboxylate complex.
 43. The method of claim 42, whereinthe filter aid is diatomaceous earth.
 44. The method of claim 42,wherein the filter aid is pearlite.
 45. The method of claim 42, furthercomprising reinforcing material selected from the group consisting ofhydrophilic fibers, hydrophobic fibers, and comminuted plant material.46. A method of circulating a hydraulic fracturing fluid in a welborepenetrating a subterranean formation, comprising: (a) providing ahydraulic fracturing fluid comprising water or an aqueous solution,water soluble crosslinkable polymer, a crosslinking agent, and a filteraid; (b) circulating the hydraulic fracturing fluid in the wellbore. 47.The method of claim 46, wherein the filter aid is selected from thegroup consisting of diatomaceous earth, perlite, glass beads, magnesiumsilicate, solid thermoplastic or thermoset polymer beads, talc, andcalcium silicate.
 48. The method of claim 47, wherein the polymer is ana carboxylate-containing polymer, and the crosslinking agent is selectedfrom the group consisting of chromium (III) carboxylate complexes,aldehydes, dialdehydes, formaldehydes, glutaraldehyde, dichromates,titanium chelates, phenols, substituted phenols, ethers, aluminumcitrate, and aluminates.
 49. The method of claim 48, wherein the filteraid comprises at least one of diatomaceous earth or pearlite.
 50. Themethod of claim 49, wherein the polymer comprises a low molecular weightpolymer having a molecular weight less than 500,000, and a highmolecular weight polymer having a molecular weight of at least 500,000.51. The method of claim 49, wherein the polymer is a water soluble,carboxylate containing acrylamide, and the crosslinking agent is achromium (III) carboxylate complex.
 52. The method of claim 51, whereinthe filter aid is diatomaceous earth.
 53. The method of claim 51,wherein the filter aid is pearlite.
 54. The method of claim 51, furthercomprising reinforcing material selected from the group consisting ofhydrophilic fibers, hydrophobic fibers, and comminuted plant material.55. A method of modifying a hydraulic fracturing fluid circulating in awellbore penetrating a subterranean formation, comprising: (a)introducing a water soluble crosslinkable polymer, crosslinking agent,and filter aid to the circulating hydraulic fracturing fluid.
 56. Themethod of claim 55, wherein the filter aid is selected from the groupconsisting of diatomaceous earth, perlite, glass beads, magnesiumsilicate, solid thermoplastic or thermoset polymer beads, talc, andcalcium silicate.
 57. The method of claim 56, wherein the polymer is ana carboxylate-containing polymer, and the crosslinking agent is selectedfrom the group consisting of chromium (III) carboxylate complexes,aldehydes, dialdehydes, formaldehydes, glutaraldehyde, dichromates,titanium chelates, phenols, substituted phenols, ethers, aluminumcitrate, and aluminates.
 58. The method of claim 57, wherein the filteraid comprises at least one of diatomaceous earth or pearlite.
 59. Themethod of claim 58, wherein the polymer comprises a low molecular weightpolymer having a molecular weight less than 500,000, and a highmolecular weight polymer having a molecular weight of at least 500,000.60. The method of claim 58, wherein the polymer is a water soluble,carboxylate containing acrylamide, and the crosslinking agent is achromium (III) carboxylate complex.
 61. The method of claim 60, whereinthe filter aid is diatomaceous earth.
 62. The method of claim 60,wherein the filter aid is pearlite.
 63. The method of claim 55, whereinthe water soluble crosslinkable polymer, crosslinking agent, and filteraid, are all in solid form.